Mich. Comp. Laws § 123.814

Sec. 4. Two or more counties, cities, villages, or townships adjacent to each other may join together, by contract or by the establishment of an intermunicipal police authority, for the purposes of providing police services to the respective counties, cities, villages, and townships. The contracts or intermunicipal police authorities shall be approved by the governing bodies of the counties, cities, villages, and townships; shall be administered by a commission established in accordance with the agreements; and shall contain provisions relative to apportionment of the costs of the services among the counties, cities, villages, or townships making the agreements.